Conventionally, computer aided diagnosis (CAD) systems detecting and outputting a site of abnormalities from medical images scanned by an X-ray CT (Computed Tomography) apparatus, an MRI (Magnetic Resonance Imaging) apparatus, ultrasound image diagnostic apparatus, etc. have been developed. For example, in case of targeting a blood vessel, a method for calculating an index such as a stenosis rate by automatically detecting the blood vessel stenosis has been proposed (for example, see Patent Literature 1). PTL 1 describes a blood vessel stenosis rate analysis system calculating a local stenosis rate by collecting information about blood vessel shapes such as a blood vessel core line and a blood vessel contour point on a blood vessel orthogonal cross section and correcting blood vessel torsion based on the collected information.
Utilizing such a technique for computerized image diagnosis, it is hoped that abnormalities such as a stenosis can be automatically detected also for the spinal canal.